DK-AS No. 112,649 discloses a revetment to be located on the inclined surfaces of moles and breakwaters. This revetment is formed by a plurality of loose blocks loosely leaning against each other and provided with water penetration holes. A revetment formed by these blocks is indeed water-permeable, but not coherent and flexible. The flexibility is a desired feature because it is necessary that the revetment may be quickly adjusted to the base on which it rests. When the coating cannot keep up quickly enough with the base where said base is washed away, it breaks up rather quickly on account of the waves. It is not sufficient to locate the blocks of the revetment relatively loosely relative to each other, since the block, the base of which is washed off, leaves an opening in the revetment. From this opening, the wash of the waves may easily break up said revetment.
DE-OS No. 26 34 586 discloses a revetment formed by a plurality of plate bodies located side by side, and which may be placed directly on the ground. However, this revetment is not suited for coast protection, firstly because the plate bodies comprise no water penetration holes and secondly because it is not flexible. The projections located on the plate bodies are intended for a rigid locking together of two bodies, thus providing a coherent revetment, but the latter is not flexible.